Can a simple blood test detect cancer before symptoms appear? Liquid biopsy and multicancer early detection (MCED) tests are reshaping how doctors think about cancer screening. New research suggests these blood-based tests could significantly increase early-stage cancer diagnoses while reducing late-stage disease, particularly for hard-to-detect cancers like pancreatic, lung, and colorectal cancer. Here’s what patients need to know about how liquid biopsies work, what’s currently FDA-approved, and the benefits and limitations of this emerging technology.

A new simulation study suggests that blood tests capable of screening for multiple cancers at once could dramatically shift when cancers are caught. Modeling 5 million US adults aged 50–84 across 14 solid tumors, researchers found that adding annual multicancer early detection (MCED) blood tests to usual care increased early-stage cancer diagnoses by 10–34% and cut late-stage diagnoses by 45% over a decade. The biggest drops in advanced disease were seen in lung, colorectal, and pancreatic cancers, cancers that are often deadly when found late.

For patients and health systems, this means potentially catching lethal tumors that currently lack robust screening options before they become untreatable, improving survival while reducing the intensity and cost of treatment.

The Science: What Liquid Biopsy Actually Tests For

A liquid biopsy is a blood test that looks for signs of cancer in your blood without needing surgery or a traditional tissue biopsy. Instead of removing a piece of tumor tissue, doctors draw blood and analyze it for cancer markers such as circulating tumor cells (CTCs), fragments of tumor DNA (ctDNA), and other cancer-related substances that tumors shed into the bloodstream.

What makes this particularly powerful is that these tests can detect cancer even when tumors are too small to see on imaging and before any symptoms appear. Early-stage cancers release measurable markers into the blood months or even years before a conventional diagnosis would be possible.

From History to Modern Medicine

Detecting cancer from a blood test may seem like something out of a futuristic sci-fi movie, but the concept actually began in the 19th century. In 1869, an Australian scientist, Thomas Ashworth, discovered circulating tumor cells in the blood of a patient with advanced cancer. This early observation hinted at how cancer spreads through the body, but it took over a century before scientists recognized its diagnostic potential.

Since 2010, rapid technological advances have transformed this concept into practical clinical tools. Blood-based cancer tests now analyze multiple biomarkers, including CTCs, ctDNA, exosomes, tumor platelets, microRNAs, and circulating RNA.

FDA-Approved Blood Tests for Cancer: What's Available Now

The FDA approved its first liquid biopsy test, CellSearch, in 2013 for monitoring patients with metastatic breast, colon, and prostate cancer. Since then, the field has advanced rapidly:

• 2016: Cobas EGFR Mutation Test v2 approved for lung cancer
• 2020: Guardant360 CDx and FoundationOne Liquid CDx approved for broad profiling of solid tumors
• 2024: Shield approved as the first blood-based screening tool for average-risk colorectal cancer

Beyond early detection, these tests help predict whether a tumor is likely to return, assess how well treatment is working, and forecast patient outcomes.

Multicancer Early Detection (MCED) Tests: One Blood Draw, Multiple Cancers

Currently, routine screening is only recommended for four main cancer types: breast, cervical, colorectal, and lung cancer. This leaves most cancers without early detection options. MCED tests aim to change that by screening for many different cancers with a single blood draw.

These tests analyze fragments of DNA circulating in the blood, looking for cancer-associated patterns such as mutations, DNA fragmentation patterns, and changes in DNA methylation (chemical modifications to DNA that can indicate cancer). Early studies show these tests are highly specific, meaning false positives are uncommon, though their ability to detect cancer varies by stage. Detection rates are lower in early-stage disease and higher in more advanced cancers. Many platforms can also identify the likely tissue of origin, pointing doctors toward where the cancer may be located.

What Recent Studies Show

Recent real-world data from the PATHFINDER 2 study at Oregon Health and Science University (OHSU) demonstrate the practical impact of MCED testing. Adding the Galleri MCED test to standard screenings increased the number of screen-detected cancers more than sevenfold. Most cancers identified were found at early stages, and about three-quarters were cancers that have no existing screening tests.

However, experts emphasize that major questions remain: How should doctors confirm a positive MCED result? Which populations should be tested and how often? How will the balance of earlier diagnoses, false positives, and possible overdiagnosis translate into long-term benefit, harm, and cost at a population level?

Why This Matters: The Impact of Early Detection

For cancer, early detection makes a critical difference in patient outcomes. Finding cancer early does not just improve survival and quality of life; it also reduces the massive financial burden of treatments that become far more expensive when cancer is caught late.

Traditional tissue biopsy remains the gold standard for cancer diagnosis, but liquid biopsy's non-invasive nature makes it ideal for early detection and continuous monitoring of tumor progression.

Current Barriers to Blood-Based Cancer Screening

1. Biological and technical limitations: In early stages, tumors sometimes do not shed enough material into the blood to be detected, which can lead to missed cancers. Additionally, not all DNA in blood comes from cancer; some comes from normal blood cells that naturally accumulate genetic changes over time. This creates background "noise" that requires sophisticated analysis to filter out. Results can also vary depending on how blood samples are collected, handled, and analyzed.
2. Clinical validation: Strong evidence showing that these tests improve survival, reduce unnecessary treatment, and are cost-effective compared with standard care is still emerging. Positive results from liquid biopsy require follow-up imaging, and the best approach for this is not yet clearly defined. Many tests also detect genetic changes that fall outside current treatment guidelines, leaving doctors uncertain about how to respond.
3. Access and equity barriers: High costs, limited insurance coverage, and unclear reimbursement pathways restrict access. The tests require rapid sample transport, specialized processing, and advanced sequencing facilities, resources often unavailable in community or under-resourced settings. Unfamiliarity among clinicians and hesitation from payers and regulators further slow adoption. Without intentional efforts to address affordability and health care disparities, access may remain uneven, potentially widening existing cancer inequities.

Do I Need a Liquid Biopsy?

Whether a liquid biopsy is right for you depends on your individual situation, family history, and risk factors. These tests are not yet part of standard screening recommendations for the general population.

For MCED tests that screen multiple cancers at once, clinical trials are ongoing, and guidelines for their use are still being developed.

If you are interested in liquid biopsy testing, talk to your doctor. Your physician can help you understand whether these tests are appropriate for your situation, discuss potential benefits and limitations, explain what a positive or negative result would mean, and guide you through any necessary follow-up.

Conclusion: The Promise and Reality of Blood-Based Cancer Detection

So, what is a liquid biopsy? It is a blood test that analyzes cancer markers circulating in your bloodstream to detect, monitor, and guide treatment for cancer, all without invasive surgery. The science shows promise: recent studies suggest these tests could shift hundreds of thousands of cancers toward earlier, more treatable stages and catch cancers that currently have no screening options.

However, liquid biopsy is not a magic bullet. While FDA-approved tests are already helping patients with specific cancers, multicancer screening tests are still emerging. Questions remain about how to best use them, who should get tested, and how to balance benefits against risks like false positives and overdiagnosis. As evidence builds and technology improves, these blood tests may become a routine part of how we catch cancer early and save lives.

Works Discussed

1. Chhatwal, J., Xiao, J., ElHabr, A. K., Tyson, C., Cao, X., Raoof, S., Fendrick, A. M., Ozbay, A. B., Limburg, P., Beer, T. M., Briggs, A., & Deshmukh, A. A. (2025). The impact of multicancer early detection tests on cancer stage shift: A 10-year microsimulation model. Cancer, 131(22), e70075. https://doi.org/10.1002/cncr.70075
2. Connal, S., Cameron, J. M., Sala, A., Brennan, P. M., Palmer, D. S., Palmer, J. D., Perlow, H., & Baker, M. J. (2023). Liquid biopsies: the future of cancer early detection. Journal of translational medicine, 21(1), 118. https://doi.org/10.1186/s12967-023-03960-8
3. Joshi, P., Gogte, P., Pawar, P., Gurav, M., Iyer, R., Singh, S., Hatkar, S., Shetty, U., Nair, A., Mulay, M., Jaiswar, S., Pai, T., Deshpande, G., Karnik, N., Shah, P., Arora, A., Juneja, A., Desai, S., Shetty, O., & Shet, T. (2025). Implementation of circulating tumor DNA (ctDNA) testing in precision oncology: A four-year experience from a tertiary cancer center in India. The journal of liquid biopsy, 9, 100319. https://doi.org/10.1016/j.jlb.2025.100319
4. Kasi P. M. (2023). Types of Liquid Biopsies: Understanding the Different Lenses Through Which They Can Detect Cancer. The oncologist, 28(4), 281–282. https://doi.org/10.1093/oncolo/oyad006
5. Ma, L., Guo, H., Zhao, Y. et al. Liquid biopsy in cancer: current status, challenges and future prospects. Sig Transduct Target Ther 9, 336 (2024). https://doi.org/10.1038/s41392-024-02021-w
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